Plastics, or polymers, are used in a variety of products and applications ranging from the simple pen to the complicated wing of an aircraft. Different types of plastic, or polymers, as they are technically known, generally have different mechanical, chemical, and electrical properties that allow plastics to be used in many applications. Plastics are typically formed into a product through a molding process, such as extrusion, injection molding, sheet molding, or blow molding. For example, plastics are used extensively in the computer and semiconductor industry in a wide variety of applications. One such application is the encapsulation of semiconductor devices, particularly integrated circuits. Encapsulating a semiconductor device in plastic materials protects the device from environmental damage and also provides structural strength to the semiconductor device.
Conventional molding systems and processes suffer from numerous disadvantages. A disadvantage of some conventional systems that use a thin film, such as those used in "3P technology" molding processes, is that the film for prepackaging pencils of a molding material often restricts the flow of the molding material into a mold cavity. The restriction may cause turbulence that entraps air and may also cause the associated mold cavity to be under-filled with the molding material. The under-filled condition or the air contained in the molding material may form internal voids in the final molded product. Internal voids are bubbles and clusters of bubbles or voids in the molded product that affect the intended use of the molded product.
Internal voids often degrade the mechanical, electrical, and chemical properties, as well as the appearance, of the molded product. In the case of encapsulated semiconductor devices, internal voids reduce the reliability of the package because they allow moisture to accumulate within the voids. This moisture may cause corrosion of the semiconductor device and may promote cracking when the encapsulated semiconductor device is subjected to additional processing, such as vapor phase reflow or a similar process.